000
acus01 kwns 201632
swody1
Storm Prediction Center ac 201630
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
1130 am CDT Monday may 20 2013
Valid 201630z - 211200z
..there is a MDT risk of severe thunderstorms for eastern/central OK...N-cntrl
Texas...northwestern Arkansas...southern MO...far southeastern Kansas...
..there is a slight risk of severe thunderstorms from the upper MS valley/central
Great Lakes to the Southern Plains...
..srn plains to Ozark Plateau...
Overall forecast scenario remains similar to earlier outlooks with
only minor overall changes to individual hazard probabilities.
Middle-level speed maximum /65 knots at 500 mb in the 12z abq radiosonde observation/ attendant
to the shortwave impulse over the Lee of the southern rockies will
overspread most of OK to the lower MO valley by early evening.
Trailing portion of cold front has become slow-moving from southeastern Kansas
to southwestern OK...intersecting a dryline that will become well
established S/southwestward across the Texas Big Country to the eastern Edwards
Plateau by late afternoon. Scattered thunderstorms will initiate along these
boundaries by mid-afternoon. Morning convection-allowing model
guidance are insistent that this activity will rapidly grow upscale
into numerous line segments...surging eastward this evening within a
strongly unstable environment.
Initial thunderstorms will become supercelluar quickly with very large hail
likely as hodographs/instability will be quite favorable...along
with a few tornadoes. The greatest risk for a couple of strong
tornadoes should exist from S-central into east-central OK. But with
predominant southwesterly component to low-level flow and moderate 0-1 km
shear...overall tornado intensity/longevity may be
tempered...especially with convection expected to grow upscale so
quickly. Nevertheless...this growth should yield bowing linear
segments capable of swaths of widespread damaging winds...large hail
and a few tornadoes.
..mid/upper-MS valley to central Great Lakes...
Primary change has been to expand damaging wind probabilities east/northeastward
for this afternoon and evening. In the wake of convection
yesterday...low-level moisture plume has become confined from lower
Michigan S/sswd to the confluence of the MS/Ohio rivers. But plentiful
heating is occurring to the north of this plume will yield a recovering
air mass downstream of a thunderstorm cluster approaching central MO. This
activity should grow upscale along the edge of the instability
axis...with additional linear segments emanating east/northeastward from the
Ozark Plateau later today. Swaths of damaging winds...large hail and
a couple of tornadoes will be possible.
Farther N/NW...scattered thunderstorms are expected to form over lower Michigan
and in parts of the upper Midwest in association with an upper-level
low centered over eastern South Dakota. Buoyancy will be strongest over lower Michigan
within the low-level moisture plume characterized by middle to upper
60s surface dew points. In the upper Midwest...pockets of robust
surface heating will support at least modest instability and with
strong unidirectional wind profiles...setup could a few organized
thunderstorm clusters. A mix of isolated severe hail/wind should be the
primary threats.
.Grams/Rogers.. 05/20/2013
Mesoscale Discussion
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acus11 kwns 201634
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 201634
miz000-inz000-201730-
Mesoscale discussion 0725
National Weather Service Storm Prediction Center Norman OK
1134 am CDT Monday may 20 2013
Areas affected...lower Michigan
Concerning...severe potential...watch likely
Valid 201634z - 201730z
Probability of watch issuance...80 percent
Summary...coverage of thunderstorms should increase through the early
afternoon across western lower Michigan...and may eventually consolidate and
spread eastward over the remainder of lower Michigan later this afternoon. An
initial threat of damaging wind gusts...large hail...and perhaps a
brief/weak tornado will exist as activity remains
semi-discrete...but should evolve into primarily a damaging wind threat
with time. A ww will likely be needed within the next hour.
Discussion...strong heating is occurring across lower Michigan within a
moist boundary layer...characterized by surface dew points in the upper
60s f...contributing to estimated MLCAPE values of 1500-2500 j/kg. A
ribbon of midlevel moisture preceding a large northern plains trough was
noted on water vapor moving eastward across Lake Michigan. As this intersects
weak low-level convergence along a developing surface trough near the
Eastern Shore of Lake Michigan...thunderstorms should rapidly develop. Moderately
strong but unidirectional vertical wind profiles oriented nearly
parallel to initiating line should promote multiple cell
interactions initially...before consolidation into clusters or a
qlcs occurs. This should propagate eastward across lower Michigan...posing a
primary threat of damaging winds...although some hail threat will also
exist given the degree of instability present.
.Rogers/Kerr.. 05/20/2013
..please see www.Spc.NOAA.Gov for graphic product...
Attention...WFO...DTX...apx...iwx...GRR...
Latitude...Lon 42648280 42158325 41898399 41758500 42018579 42928620
43848603 44748600 45378534 45668491 45698433 45308361
43938284 42648280
